Systems for the electrical stimulation of the retina by a retinal electrode array held against the retina are known. See, for example, U.S. Pat. No. 5,935,155, incorporated herein by reference in its entirety, where a system for capturing a video image, transferring the image wirelessly into a living body and applying the image to a retinal electrode array is shown.
During video stimulation, subjects often report unpleasantly high brightness, or physical discomfort, when the camera input is very bright (the video levels are high throughout the entire image and discomfort can be felt also on single electrodes). Therefore, there is a need to avoid discomfort while maintaining a bright percept from stimulation.
Additionally, when multiple electrodes on the retinal implant are stimulating at the same time, e.g., when presenting a pattern to the subject, electric charges often interact with each other and create a much brighter pattern than intended. Therefore, also in this case, there is a need to compensate for the interactions, so that images or patterns can be presented with more consistent contrast and brightness and also eliminate discomfort.